Optical switch assembly with flex plate and method for making

ABSTRACT

An optical switch and method for assembling are described. Optical arrays are mounted on a flex plate with an interface between them. The direction of certain forces on the flex plate allows coupling/decoupling of the optical arrays. The flex plate includes an area which exhibits a different flex profile than the remainder of the flex plate and that is located beneath the optical arrays interface. Flexing of the flex plate optically couples the optical arrays. A tool with grooves is used to align the optical arrays relative to each other. The tool uses grooves and spheres to mate with the optical arrays in such a way as to provide an appropriate interface between the optical arrays.

This is a divisional application of U.S. application Ser. No. 10/022,726filed Dec. 20, 2001 now U.S. Pat. No. 6,810,162 which claims priorityfrom provisional application Ser. No. 60/257,020 filed Dec. 20, 2000,such applications being incorporated herein by reference.

FIELD OF THE INVENTION

The present invention related to a frustrated total internalreflection/total internal reflection (FTIR/TIR) optical fiber switch.

BACKGROUND

Conventional frustrated total internal reflection/total internalreflection optical fiber switches operate by displacing at least one ofthe fibers to contact, or come within less than a micron from contactwith, the other fiber (closed position) or to release contact with theother fiber (opened position). Generally, the optical fibers connect oneanother at ends which are formed transverse to the longitudinal axis ofthe fibers and coplanar to one another. In the closed position, inputlight is transmitted from one optical fiber to the other with little orno transmission loss. In the opened position, in which a gap exists ofgreater than one micron between the optical fibers, input light isreflected from one of the fibers, leading to complete or partialtransmission loss. Complete transmission loss occurs during totalinternal reflection, when light approaches a dielectric interface at orabove a critical angle and is thereby suppressed from being transmittedto the other optical fiber. When the angle is below the critical angle,or the distance between the optical fibers is sufficiently small, someinput light may cross the gap between the optical fibers and therebyfrustrate the total internal reflection. An example of such aconventional optical switch is described in U.S. Pat. Nos. 5,390,266 and4,176,908.

SUMMARY

The invention provides an optical switch that includes first and secondoptical arrays separated by an interface, and a support structure uponwhich the optical arrays are mounted. The support structure includes anarea which has a flexing profile that differs from the remainder of thesupport structure such that upon the operation of force on the supportstructure the optical arrays are optically coupled or decoupled.

The invention also provides an optical switch that includes first,second, third, fourth and fifth optical arrays and a support structureupon which the first, second and third optical arrays are mounted. Thethird optical array is interposed between the first and second opticalarrays, the first and third optical arrays are separated by a firstinterface, and the second and third optical arrays are separated by asecond interface. The support structure includes a pair of areas whicheach have a flexing profile that differs from the remainder of thesupport structure. The fourth optical array is positioned transverse tothe first and third optical arrays in the vicinity of the firstinterface and the fifth optical array is positioned transverse to thesecond and third optical arrays in the vicinity of the second interface.

The invention further provides a method for assembling an opticalswitch. The method includes aligning at least a first optical array anda second optical array relative to one another with an alignment tool,positioning the at least first and second optical arrays on a supportstructure, immobilizing the at least first and second optical arraysrelative to the support structure, and removing the tool from the atleast first and second optical arrays.

The foregoing and other advantages and features of the invention will bemore readily understood from the following detailed description of theinvention, which is provided in connection with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1–3 is a side view of an optical switch assembly constructed inaccordance with an embodiment of the invention.

FIG. 4 is a perspective view of the flex plate of the optical switchassembly of FIG. 1.

FIG. 5 is a side view of an optical switch assembly constructed inaccordance with another embodiment of the invention.

FIG. 6 is a side view of an optical switch assembly constructed inaccordance with another embodiment of the invention.

FIGS. 7–9 is a side view of an optical switch assembly constructed inaccordance with another embodiment of the invention.

FIG. 10 is a schematic drawing of a conventional optical system.

FIG. 11 is a schematic drawing of an optical system utilizing theoptical switch assembly of FIG. 7 in accordance with another embodimentof the invention.

FIGS. 12–13 are side views showing the assembly of an optical switchassembly in accordance with another embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1–4, in which like numerals designate like elements,an optical FTIR/TIR switch assembly 10 is shown including a first angledoptical array 11, a second angled optical array 21, and a flexiblesupport structure, such as a flex plate 40. The first optical array 11includes a support structure, such as a chip 12, that has a face 20 andfirst and second surfaces 14, 18. The first surface 14 includes at leastone first surface groove 16. The second optical array 21 includes asupport structure, such as a chip 22, that has a face 30 and first andsecond surfaces 24, 28. The first surface 24 has at least one firstsurface groove 26. The chips 12, 22 are preferably formed of silicon.

The flex plate 40 includes a trench 42 which is preferably formedthrough isotropic etching. Each of the optical arrays 11, 21 is mountedon the flex plate 40, which is preferably formed of single crystalsilicon, such that there is an interface 25 (e.g., a gap) between thefaces 20, 30 and such that the interface 25 is positioned above thetrench 42. The first and second arrays 11, 21 are positioned and adheredto the flex plate 40. Preferably an adhering material is utilized toimmobilize the first and second arrays 11, 21.

Upon each of the optical arrays 11, 21 are mounted one or more opticalfibers, which are preferably formed of silica. As shown, an opticalfiber 32 is mounted within the groove 16 of the chip 12, and acorresponding optical fiber 36 is mounted within the groove 26 of thechip 22. The optical fibers 32, 36 have endfaces 34, 38, respectively,that are angled at an angle greater than a total internal reflectionangle of the optical fiber material. The optical fibers 32, 36 may beadhered to the grooves 16, 26 through the use of an adhering material ormechanism (not shown). Any suitable adhering material or mechanism maybe used, such as, for example, ultraviolet curable epoxy, solder,aluminum-oxide direct thermal compression bonding, or sol-gel or spin-onglass.

The optical switch assembly 10 is shown in FIGS. 2–3 in, respectively,an opened and a closed state. In FIG. 2, forces are directed upon theflex plate 40 at certain locations. Specifically, a force in a directionB is directed toward the flex plate 40 generally near the trench 42.Further, forces in a direction A are directed away from the flex plate40 at ends of the flex plate 40. The forces tend to allow the flex plate40 to flex such that its ends move generally in direction A. Since thechips 12, 22 are mounted on the flex plate 40, such movement results inthe endfaces 34 and 38 of the optical fibers 32, 36 moving apart fromone another, thus opening the optical switch assembly 10.

FIG. 3 illustrates the optical switch assembly 10 in the closedposition. As shown, force is directed away from the flex plate 40 in thedirection A in the general vicinity of the trench 42, while forces aredirected toward the flex plate 40 at its ends in the direction B.Through this arrangement of forces, the flex plate 40 tends to push theendfaces 34, 38 together, thereby closing the optical switch assembly10.

As noted above, the trench 42 of the flex plate 40 is preferablyisotropically etched. The trench 42 should preferably extend across theflex plate as shown in FIG. 4. It is preferred that the trench 42 has asmooth sidewall 43 to prevent any localized mechanical stress during thepreviously described flexing operations. It is to be understood that asuitable flex plate 40 includes an area, such as the trench 42 or anyother similar structure, that has a different flexing capability orprofile relative to the remaining portion of the flex plate 40.

FIG. 5 illustrates another aspect of the invention with reference to anoptical switch assembly 100 which includes a first optical array 111 anda second optical array 121 positioned on a flex plate 140. The opticalarrays 111, 121 are each mounted on spheres 139. Specifically, the firstoptical array 111 has a second surface 118 including one or more grooves119 and the second optical array 121 has a second surface 128 having atleast one groove 129. The flex plate 140 also has a plurality of grooves141 on an upper surface thereof which mate with the grooves 119, 129.Spheres 139 seat within the grooves 141. As shown, the groove 129 iselongated relative to the grooves 141. Elongation of the groove 129relative to its mating groove 141 allows the second optical array 121 tomove in a direction C relative to the first optical array 111 duringassembly, thus allowing adjustment of the gap between the endfaces 34,38. Once the gap has been properly adjusted, the optical arrays 111, 121are then immobilized relative to the flex plate 140. Preferably, thegrooves 119, 129, 141 are anisotropically wet etched with potassiumhydroxide or other suitable etchant material.

FIG. 6 illustrates another optical switch assembly 200, which includesthe first optical array 12, the second optical array 22, and a flexplate 240. The flex plate 240 is a silicon-on-insulator (SOI) waferwhich includes a pair of silicon layers 244, 248 sandwiching aninsulator layer 246. The trench 42 is isotropically etched in thesilicon layer 244 by etchant materials. The insulator layer 246 ispreferably formed of a material which is resistant to the etchantmaterials used to etch the silicon layer 244. The proper depth of thetrench 42 is obtained by the position of the insulator layer 246, whichsuppresses etching of the trench 42.

With reference to FIGS. 7–9, another aspect of the invention is shownwith reference to an optical switch 300 which includes a first opticalarray 211, a second optical array 221, a third optical array 231, afourth optical array 261, a fifth optical array 271, and a flex plate280. The first optical array 211 includes a chip 212, which has a firstsurface 214, a second surface 218, and a face 220. The second opticalarray 221 includes a chip 222, which has a first surface 224, a secondsurface 228, and a face 230. The third optical array 231 is positionedbetween the first and second optical arrays 211, 221, and includes achip 232, which has a first surface 234, a second surface 238, and apair of faces 237, 239. The face 237 mates with the face 220 of thefirst optical array 211, while the face 239 mates with the face 230 ofthe second optical array 221.

The first surfaces 214, 224, 234 each include at least one groove 216,226, 236, respectively. An optical fiber 250 is positioned within thegroove 216, an optical fiber 252 is positioned within the groove 226,and an optical fiber 254 is positioned within the groove 236. There isan interface 256 that extends between the face 237 of the chip 232 andthe endface of its respective optical fiber 254 and the face 220 of thechip 212 and the endface of its respective optical fiber 250. Further,there is an interface 258 that extends between the face 239 of the chip232 and the endface of optical fiber 254 and the face 230 of the chip222 and the endface of its respective optical fiber 252.

The fourth and fifth optical arrays 261 and 271 are on-edge opticalarrays which collect light which has been reflected from the interfaces256, 258. The fourth optical array 261 includes a chip 262, having agroove 264, and an optical fiber 266. The fifth optical array 271includes a chip 272, having a groove 274, and an optical fiber 276. Thefourth optical array 261 is positioned transverse to the alignment ofthe first, second and third optical arrays 211, 221, 231 and generallyin the vicinity of the interface 256. The fifth optical array 271 ispositioned transverse to the alignment of the first, second and thirdoptical arrays 211, 221, 231 and generally in the vicinity of theinterface 258.

The flex plate 280 includes a pair of etched trenches 282, 284. Each ofthe trenches 282, 284 is positioned beneath one of the interfaces 256,258. With specific reference to FIG. 8, by directing a force in thedirection A away from the flex plate 280 in the general vicinity of thethird optical array 232, and by concurrently directing forces in thedirection B toward the flex plate 280 at its edges, light which is inputfrom a light source 286 is transmitted along the optical fibers 250,254, and 252 to an output destination 288. If instead, as shown in FIG.9, a force is directed in the direction B toward the flex plate 280 inthe general vicinity of the third optical array 232, and forces aredirected away from the flex plate 280 in the direction A at the plate's280 edges, the interfaces 256, 258 are misaligned to such an extent asto suppress light from being transmitted through the optical fibers 250,254, and 252. Instead, light from the light source 286 may be sentthrough the optical fiber 250, reflected at the gap between the opticalfiber 250 and the optical fiber 254, collected by the optical fiber 266,and transmitted to the output destination 288. In addition, light from asecond light source 290 concurrently may be sent through the opticalfiber 252, reflected at the gap between the optical fiber 252 and theoptical fiber 254, collected by the optical fiber 276, and transmittedto a second output destination 292.

The optical switch assembly 300 is particularly useful for ring networksin which a switch must be continuously connected and disconnected from adata ring. A conventional ring network 350, shown in FIG. 10, includes aplurality of nodes 302 in communication with each other. FIG. 11illustrates the inclusion of the optical switch assembly 300 in a dataring 400. Light from a light source 286 which is within the data ring400 is transmitted to the optical switch 300 and reflected into theoptical array 262 and sent to the output destination 288, which in thisinstance is one of the nodes 302. Further, light from a light source 290which is within the data ring 400 also is transmitted to the opticalswitch 300, reflected into the optical array 272 and sent to the outputdestination 292, which in this instance is the same node 302.

With reference to FIGS. 12–13, next will be described a method ofassembling an optical switch assembly in accordance with an embodimentof the invention. The optical switch assembly shown in FIGS. 12–13includes a first optical array 312 and a second optical array 322. Thefirst optical array 312 includes a first surface 314 and a secondsurface 318. At least one groove 316 is located in the first surface314, and at least one pit 317 is also located in the first surface 314.The second optical array 322 includes a first surface 324 and a secondsurface 328. At least one groove 326 is located in the first surface324, and at least one pit 327 is further located in the first surface324. The second surfaces 318, 328 are to be mounted on the flex plate40.

A tool 330, having at least a pair of pits 334 in a first surface 332 isused to align the first optical array 312 relative to the second opticalarray 322. Spheres 336 are positioned within the pits 334 and theoptical arrays 312, 322 are moved so that the spheres 336 concurrentlyfit within the pits 317, 327, thereby adjusting the position of thefirst optical array 312 with respect to the second optical array 322.The spheres 336 may be adhered to the pits 334 with an adhesive material338. Once proper position has been obtained, the optical arrays 312, 322are immobilized relative to the flex plate 40 and the tool 330 isremoved.

While the invention has been described in detail in connection with thepreferred embodiments known at the time, it should be readily understoodthat the invention is not limited to such disclosed embodiments. Rather,the invention can be modified to incorporate any number of variations,alterations, substitutions or equivalent arrangements not heretoforedescribed, but which are commensurate with the spirit and scope of theinvention. For example, although the flex plate 40 has been shown tohave a semicircularly-shaped trench 42, it should be understood that thetrench may be any suitable shape capable of localizing the flexingpotential of the flex plate 40. Also, instead of a trench 42, the areawith a different flex profile from the remainder of the flex plate 40may be formed with a hinge or biasing member or other suitablemechanism. Further, while the tool 330 has been illustrated to showalignment of one optical array with another, it is to be understood thatthe tool 330 may be modified to align three optical arrays, such asoptical arrays 211, 221, 231 shown in FIG. 7, and the remaining opticalarrays 261 and 271 may be separately aligned. Accordingly, the inventionis not to be seen as limited by the foregoing description, but is onlylimited by the scope of the appended claims.

1. A method for assembling an optical switch, comprising: aligning atleast a first optical fiber array and a second optical fiber arrayrelative to one another with an alignment tool; positioning said atleast first and second optical fiber arrays on a support structure,wherein said positioning comprises locating on said support structuresaid at least first and second optical fiber arrays with an interfacetherebetween, wherein said locating is such that upon certain forcesdirected in certain directions and at certain locations of said supportstructure said interface is lessened and said at least first and secondoptical fiber arrays are optically coupled; immobilizing said at leastfirst and second optical fiber arrays relative to said supportstructure; and removing said tool from said at least first and secondoptical fiber arrays.
 2. The method of claim 1, wherein said aligningcomprises: mating at least a first groove on said tool with at least afirst groove on said first optical fiber array; mating at least a secondgroove on said tool with at least a second groove on said second opticalfiber array; and positioning a sphere within said mated first groovesand positioning a sphere within said mated second grooves.
 3. The methodof claim 1, wherein said immobilizing comprises adhering said at leastfirst and second optical fiber arrays to said support structure.
 4. Amethod for assembling an optical switch, comprising: aligning at least afirst optical fiber array and a second optical fiber array relative toone another with an alignment tool; positioning said at least first andsecond optical fiber arrays on a support structure; immunobilizing saidat least first and second optical fiber arrays relative to said supportstructure; and removing said tool from said at least first and secondoptical fiber arrays, wherein said aligning comprises aligning saidfirst and second optical fiber arrays relative to a third optical fiberarray, said third optical fiber array being interposed between saidfirst and second optical fiber arrays.
 5. The method of claim 4, whereinsaid positioning comprises locating on said support structure saidfirst, second and third optical fiber arrays with a first interfacebetween said first and third optical fiber arrays and a second interfacebetween said second and third optical fiber arrays.
 6. The method ofclaim 5, wherein said locating is such that upon certain forces directedin certain directions and at certain locations of said supportstructure, said first and second interfaces are lessened and said atleast first and second optical fiber arrays are optically coupled withsaid third optical fiber array.
 7. The method of claim 4, wherein saidimmobilizing comprises adhering said first, second and third opticalfiber arrays to said support structure.
 8. A method for assembling anoptical switch, comprising: aligning at least a first optical array anda second optical array relative to one another with an alignment tool,said aligning comprising: mating at least a first groove on said toolwith at least a first groove on said first optical array; mating atleast a second groove on said tool with at least a second groove on saidsecond optical array; and positioning a sphere within said mated firstgrooves and positioning a sphere within said mated second grooves;positioning said at least first and second optical arrays on a supportstructure; immobilizing said at least first and second optical arraysrelative to said support structure; and removing said tool from said atleast first and second optical rays.
 9. The method of claim 8, whereinsaid immobilizing comprises adhering said at least first and secondoptical arrays to said support structure.
 10. A method for assembling anoptical switch, comprising: aligning at least a first optical array anda second optical array relative to one another with an alignment tool:positioning said at least first and second optical arrays on a supportstructure, wherein said positioning comprises locating on said supportstructure said at least first and second optical arrays with aninterface therebetween such that upon certain forces directed in certaindirections and at certain locations of said support structure saidinterface is lessened and said at least first and second optical arraysare optically coupled; immobilizing said at least first and secondoptical arrays relative to said support structure; and removing saidtool from said at least first and second optical arrays.
 11. The methodof claim 10, wherein said immobilizing comprises adhering said at leastfirst and second optical arrays to said support structure.